The present invention relates to a magnetic tape cartridge, in which a single tape reel with magnetic tape wound thereon is rotatably housed within a cartridge case, and in which a leader pin for pulling the magnetic tape out of the cartridge case is affixed to the leading end of the magnetic tape.
In existing magnetic tape cartridges, which are being used as_storage media employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case. This magnetic tape is employed to archive data for computers, etc. Since important information has been stored, the magnetic cartridge is constructed so that problems, such as tape jamming, etc., do not occur and that the magnetic tape is not pulled out of the cartridge case unexpectedly.
Also, as shown in FIGS. 1, 4, etc., of Japanese Unexamined Patent Publication No. 11 (1999)-232838, a leader pin (tape pulling-out tool) is affixed to the leading end portion of the magnetic tape to pull the magnetic tape out of the cartridge case. This leader pin is held and pulled out by a hold member of a drive unit provided on the side of a recording-reproducing apparatus, whereby forward winding or reverse winding of the magnetic tape is performed. Uniting of the leader pin and the magnetic tape can be performed by winding the magnetic tape on the outer periphery of the tape clamp shaft portion of the leader pin and then elastically fitting a clamp member with a C cross section onto the tape clamp portion to clamp the leading end portion of the magnetic tape therebetween.
In the structure in which the leader pin is affixed to the leading end of magnetic tape as described above, the coefficient of friction between the magnetic tape and the leader pin is low and therefore there is a possibility that because of insufficient clamping force, the leader pin will be disengaged from the magnetic tape.
More specifically, in order to reduce the sliding friction between the magnetic tape and the magnetic head, there are cases where the addition of a lubricating agent to the magnetic layer of the magnetic tape, or the coating of a lubricating agent on the top surface of the magnetic tape, is performed so that the coefficient of friction is reduced. The bottom surface of the magnetic tape is also treated in the same manner. In that case, the coefficient of friction between the leader pin, formed from stainless steel, etc., and the magnetic tape varies with the type of the magnetic tape. When this coefficient of friction is low, there are cases where the clamping force of the magnetic tape with respect to the leader pin by the engagment of the clamp member onto the leader pin is reduced.
The present invention has been made in view of the points mentioned above. Accordingly, it is a primary object of the present invention to provide a magnetic tape cartridge that is capable of enhancing the clamping force of the magnetic tape with respect to the leader pin to assure reliability.
The aforementioned leader member is detachably held in the cartridge case by a lock member, called a shaft holding portion, which has an engaging function, as shown in FIG. 6 of the aforementioned Japanese Unexamined Patent Publication No. 11 (1999)-232838. It is advantageous from the viewpoint of structural simplification to employ a spring member to hold the leader member.
Therefore, if there is provided a lock member with integral upper and lower hold portions which abut the upper and lower ends of the leader pin, the assembly of the leader pin to the upper and lower cases of the magnetic tape cartridge will be enhanced. However, in forming the lock member by stamping and bending a plate spring, the manufacturing precision is reduced depending on the configuration of the lock member and there is a problem that the holding force of the lock member with respect to the leader pin will vary.
For example, consider al lock member manufactured by pressing a plate spring such as that shown in FIGS. 15 and 16. In FIG. 15, a leader pin 5 affixed to the leading end of magnetic tape 6 is pulled in and out through an opening 10 formed in the side surfaces of an upper case (not shown) and a lower case 3. Inside the opening 10, upper and lower housing recesses 20 are formed in the bottom surface of the upper case and the top surface of the lower case 3, and the upper and lower end portions of the leader pin 5 are held in the housing recesses 20. Also, a tapered lower guide portion 21 is provided from the lower housing recess 20 toward the opening 10. A lock member 50, for detachably holding the leader pin 50 in the housing recesses 20, is symmetrical in the vertical direction thereof and formed into a U-shape, as shown in FIG. 16. The lock member 50 has amounting portion 50a, which is clamped between a mounting boss 51 erected in the bottom surface of the lower case 3 and the side wall 3b of the lower case 3, along the side wall 3b. The lock member 50 also has upper and lower elastic arm portions 50b, 50b extending from the forwardly curved rear portion of the mounting portion 50a toward the opening 10. The elastic arm portions 50b, 50b have leader-pin holding portions 50c, 50c at their outer ends, respectively. The leader-pin holding portions 50c, 50c abut the upper and lower end portions of the leader pin 5, respectively. Each leader-pin holding portion 50 is bent and has an outer inclined surface which is contacted and deformed by the leader pin 5 being inserted through the opening 10, and an inner inclined surface with which the leader pin is pressed against and held in the housing recess 20.
The lock member 50 is bent into a deeply curved U-shape by pressing a plate spring, so it is difficult to accurately form an angle a (see FIG. 16) which the mounting portion 50a forms with the elastic arm portion 50b. The amount of deformation in pressing and holding the leader pin 5 varies and therefore the holding force of the lock member 50 with respect to the leader pin 5 tends to vary. In addition, the deep U-shape pressing requires a plurality of press operations and increases the number of manufacturing steps. Since the deep U-shape pressing makes the length of the elastic arm portion 50b longer and thus increases the developed area, a large quantity of plate spring material is discarded after the stamping operation. Thus, the deeply U-shaped lock member 50 is disadvantageous in terms of cost. Furthermore, when a large number of lock members 50 are stored, they are stacked and engaged with one another, if each lock member 50 has a deeply curved U-shape. Since it is difficult to separate them from each other, there is the problem that feeding them serially by a part feeder may become difficult.
On the other hand, in the mounting structure of the lock member 50 in the cartridge case 4, in which the mounting portion 50a of the lock member 50 is disposed along the side wall 3b of the lower case 3 and clamped between the side wall 3b and the mounting boss 51, that part of the metal mold which molds the gap between the mounting boss 51 and the side wall 3b will become very thin, if the lock member 50 is made thin in order to obtain proper leader-pin holding force. Because of this, there is a possibility that the thickness-reduced part of the metal mold will be damaged by pressure produced when resin is injected. It is also difficult to manufacture a metal mold having thin portions. Particularly, when the mounting boss 51 is formed high, or long along the side wall 3b, the aforementioned phenomenon becomes conspicuous.
Furthermore, when the, plate-shaped lock member 50 is assembled into the cartridge case 4, depending on the locking structure there is a possibility that the upper case cannot be closed to the lower case 3. That is, when the lock member 50 is set to the lower case 3, and the upper case is stacked on the lower case 3, the lock member 50 tilts and cannot engage with the mounting boss 51 of the upper case and abut the lower end of the mounting boss 51, and therefore the upper case cannot be closed. Particularly, a space is required around the leader pin 5 so that a leader-pin pulling-out mechanism of a drive unit can enter through the opening 10 and hold the leader pin 5. The mounting boss 51 needs to be low in height so that it does not interfere with the leader-pin pulling-out mechanism, and the mounting boss also cannot be made high from the viewpoint of the metal-mold strength described above. Therefore, there is a possibility that problems associated with the aforementioned tilting will arise.
The present invention has been made in view of the points mentioned above. Accordingly, it is a secondary object of the present invention to provide a magnetic tape cartridge which is capable of holding the leader pin in a satisfactory manner by improving the manufacturing precision, mounting performance, etc., of the spring member which detachably holds the leader pin.
To achieve the primary object of the present invention mentioned above, there is provided a first magnetic tape cartridge comprising (1) a single reel with magnetic tape wound thereon; (2) a cartridge case for rotatably housing the single reel; (3) a leader pin having a tape clamp portion on which the magnetic tape is wound; and (4) a clamp member with a C cross section that has an axial slit; wherein the leader pin is affixed to a leading end of the magnetic tape by elastically fitting the clamp member onto the tape clamp portion of the leader pin; and wherein a sheet member for enhancing a coefficient of friction is interposed at least between the magnetic tape and the tape clamp portion.
The sheet member may be stuck to the magnetic tape. This case is preferable because the uniting operation of the magnetic tape and the leader pin is easily performed.
In addition, the sheet member may be provided without being stuck to the magnetic tape. In this case, when the magnetic tape is repeatedly bent near the leader pin, as the position at which the magnetic tape is clamped varies, durability is enhanced.
The sheet member refers to flexible ribbon-like members, such as plastic sheet (polyester, etc.), plastic film, foam sheet (elastomer, etc.), laminate film, laminate paper, etc. The sheet member is selected so that the coefficient of friction between the surface of the sheet member and the leader pin becomes higher than that between the surface of the magnetic tape and the leader pin.
According to the first magnetic tape cartridge, the sheet member for enhancing a coefficient of friction is interposed at least between the magnetic tape and the tape clamp portion when the leader pin is affixed to the leading end portion of the magnetic tape by fitting the clamp member onto the leader pin. Therefore, even when the friction coefficient between the surface of the magnetic tape and the leader pin is low, the interposition of the sheet member enhances the friction coefficient between the sheet member and the leader pin and increases the clamping force of the magnetic tape with respect to the leader pin. As a result, disengagement of the leader pin from the magnetic tape can be prevented, whereby reliability can be assured.
Furthermore, the interposition of the sheet member can reinforce the magnetic tape near the tape clamp portion of the leader pin when the leader pin is pulled out and in by a drive unit.
To achieve the second object of the present invention mentioned above, there is provided a second magnetic tape cartridge comprising (1) a single reel with magnetic tape wound thereon; (2) a cartridge case, which comprises an upper case and a lower case, for rotatably housing the single reel; (3) a leader pin affixed to a leading end of the magnetic tape to pull the magnetic tape out of the cartridge case; and (4) a lock member, formed from a plate spring, for detachably locking and holding an upper end portion and a lower end portion of the leader pin; wherein the lock member comprises a mounting portion which is held by the upper and lower cases, and elastic arm portions extending from the mounting portion toward the leader pin and engageable with the upper and lower end portions of the leader pin; and wherein an interior angle that the mounting portion forms with the elastic arm portion is an obtuse angle.
The interior angle that the mounting portion of the aforementioned lock member forms with the elastic arm portion of same is 135xc2x0 or greater.
Further, an alternate embodiment of this second magnetic tape cartridge is characterized by a lock member, formed from a plate spring, for detachably locking and holding an upper end portion and a lower end portion of the leader pin; upper and lower spring type lock-member installing portions, provided in the upper and lower cases of the cartridge case, for holding the lock member; wherein the lock member comprises a mounting portion which is held by the upper and lower cases, and elastic arm portions extending from the mounting portion toward the leader pin and engageable with the upper and lower end portions of the leader pin; and wherein the upper and lower spring type lock-member installing portions hold the lock member at positions away from side walls of the lower and upper cases to the inside. It is preferable from the viewpoint of metal-mold strength that the upper and lower lock-member installing portions be formed at positions 0.4 mm or greater away from the side walls of the lower and upper cases.
In the alternate embodiment of the second magnetic tape cartridge of the present invention described above, the mounting portion of the lock member has upper and lower engagement recesses at upper and lower edges thereof. The upper and lower lock-member installing portions have upper and lower protrusions. The lock member is positioned and held by fitting the upper and lower protrusions into the upper and lower engagement recesses.
In addition, it is preferable that the lock-member installing portion be provided with inclined surfaces for guiding the lock member to the protrusion. It is also preferable that the lock member be provided with guide portions engageable with the inclined surfaces of the lock-member installing portion. By this structure, the engagement between the lock member and the lock-member installing portion can be facilitated.
In the alternate embodiment of the second magnetic tape cartridge of the present invention, it is preferable that the upper and lower lock-member installing portions have a tilt regulating portion for holding an edge, opposite from the elastic arm portions, of the mounting portion of the lock member in an erect posture. By this structure, tilting of the lock member can be prevented.
Note that when the lock member such as that described above is assembled into the cartridge case, the upper and lower cases of the cartridge case can be fastened together by tightening small screws inserted in holes formed in the upper case. In this case, the lock member is installed in the lower case. After the upper case is stacked on the lower case, they are assembled without inverting the cartridge case up and down. By this method, the assembly operation can be efficiently performed.
According to the second magnetic tape cartridge of the present invention, an interior angle that the mounting portion of the lock member forms with the elastic arm portion of the lock member is an obtuse angle. Therefore, deep curve pressing is unnecessary, manufacturing precision is enhanced, and the amount of deformation in pressing and holding the leader pin becomes constant and therefore stable leader-pin locking force is obtained. In addition, the pressing operation becomes easy and manufacturing steps are simplified. The length of the elastic arm portion is short, so the developed area is reduced and costs are decreased. Furthermore, even if a large number of lock members are stored, they are less likely to engage each other and can be serially fed by a part feeder.
According to an alternate embodiment of the second magnetic tape cartridge of the present invention, the upper and lower spring type lock-member installing portions hold the lock member at positions away from side walls of the lower and upper cases to the inside. Therefore, even if the lock member is made thin, that part of the metal mold which molds the wall surface of the cartridge case will not become thin and therefore the metal mold can be easily manufactured and damage to the metal mold can be prevented.
If engagement recesses for fitting the protrusions of the spring type lock-member installing portion are provided in the upper and lower edges of the mounting portion of said lock member, longitudinal positioning of the lock member can be simultaneously performed and therefore the accuracy of position between the lock member and the leader pin can be enhanced.
Furthermore, if the tilt regulating portion for holding the lock member in an erect posture is provided in said spring type lock-member installing portion, tilting of the lock member can be prevented, for example, when the lock member is installed in the lower case and the upper case is stacked on the lower case, while assuring a space for a leader-pin pulling-out mechanism of a drive unit. Thus, satisfactory assembly performance can be assured.
If screw holes are formed in the top surface of the upper case so that assembly can be performed without inverting the cartridge case up and down, assembly performance is further enhanced.